Radio frequency port impedance detection using concurrent radios

ABSTRACT

Technologies directed to a wireless device with RF port impedance detection using concurrent radios are described. One wireless device includes an impedance detection circuit with a bi-directional RF coupler and switching circuitry. A processing device at least two radios, at least two RF ports, and an impedance detection circuit. The impedance detection circuit is configured to measure a first receive signal strength indicator (RSSI) value of a first reflected signal. The first reflected signal corresponding to a first signal sent by one of the at least two radios. The impedance detection circuit determines that the first RSSI value exceeds a threshold. The threshold represents an impedance mismatch condition at or beyond at least one of the two RF ports. The processing device sends a first indicative of the impedance mismatch condition to a second device.

RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 16/744,947, filed Jan. 16, 2020, the entirecontents are hereby incorporated by reference.

BACKGROUND

A large and growing population of users is enjoying entertainmentthrough the consumption of digital media items, such as music, movies,images, electronic books, and so on. The users employ various electronicdevices to consume such media items. Among these electronic devices(referred to herein as endpoint devices, user devices, clients, clientdevices, or user equipment) are electronic book readers, cellulartelephones, Personal Digital Assistants (PDAs), portable media players,tablet computers, netbooks, laptops, and the like. These electronicdevices wirelessly communicate with a communications infrastructure toenable the consumption of the digital media items. In order tocommunicate with other devices wirelessly, these electronic devicesinclude one or more antennas.

BRIEF DESCRIPTION OF DRAWINGS

The present inventions will be understood more fully from the detaileddescription given below and from the accompanying drawings of variousembodiments of the present invention, which, however, should not betaken to limit the present invention to the specific embodiments, butare for explanation and understanding only.

FIG. 1A is a block diagram of a wireless device with an impedancedetection circuit where a first radio transmits a first signal accordingto one embodiment.

FIG. 1B is a block diagram of the wireless device with the impedancedetection circuit where a second radio transmits a second signalaccording to one embodiment.

FIG. 2 is a block diagram of a wireless device 200 with an impedancedetection circuit 202 with a butler matrix according to one embodiment.

FIG. 3 is a block diagram of a wireless device with an impedancedetection circuit in a frequency domain reflectometry mode according toone embodiment.

FIG. 4 illustrates operation of a bi-directional RF coupler in afrequency domain reflectometry mode according to one embodiment.

FIG. 5 illustrates a frequency domain reflectometer visualization of thebi-directional RF coupler according to one embodiment.

FIG. 6A is a graph of S-parameter measurements for a bi-directionalcoupler according to one embodiment.

FIG. 6B is a graph of S-parameter measurements for a bi-directionalcoupler with an attenuator at a coupler (CPL) port according to oneembodiment.

FIG. 7 is a block diagram of a wireless device with an impedancedetection circuit with a pair of reflective RF switches (SW_R) in anRSSI mode according to one embodiment.

FIG. 8 is a block diagram of a wireless device with an impedancedetection circuit with a pair of reflective RF switches (SW_R) in areflectometry mode according to one embodiment.

FIG. 9 is a flow diagram of a method of determining a reflectiondistance of an impedance mismatch condition according to one embodiment.

FIG. 10 is a flow diagram of a method of determining an impedancemismatch condition according to one embodiment.

FIG. 11 is a timing diagram illustrating a wireless device transmittinga frame to reserve a medium and a data frame for impedance detectionaccording to one embodiment

FIG. 12 is a block diagram of an electronic device that can beconfigured to detect impedance mismatch conditions and a physicaldistance to a location where the impedance mismatch condition occurs asdescribed herein according to one embodiment.

DETAILED DESCRIPTION

Technologies directed to a wireless device with Radio Frequency (RF)port impedance detection using concurrent radios are described. Manywireless devices used in a fixed wireless infrastructure use externalantennas to maintain flexibility in coverage and system gain for eachuse case. However, antennas may be disconnected from the radio or damageto cabling, antenna, or both may occur. Under these conditions, anetwork operations center (NOC) may only see changes in radio link-levelparameters, including receive signal strength indicator (RSSI) andthroughput parameters. Degradation due to channel deterioration may beindistinguishable from a device issue where the antenna is disconnectedor there is damage to an RF cable or the antenna itself. Degradation canalso be caused by a physical attribute of the RF cable that causesmalfunction of the RF cable. Traditionally, there is no direct feedbackfrom devices in the fixed wireless infrastructure indicating a conditionof an RF signal path external to the device. Network scalability andmaintainability can be significantly impacted by these types ofimpedance mismatch conditions. In some cases, when a wireless devicewith concurrent radios is deployed and yet only a single antenna isconnected, a second radio should be shut off to reduce power consumptionand potential interference. This may not be done properly at staging(i.e., pre-deployment configuration) by an installer since it isdifficult for the installer to know which radio to shut off, even withvisual identification of the external RF ports. The manual configurationof selecting a radio to shut down by the installer is error prone.

Aspects of the present disclosure overcome the deficiencies oftraditional wireless devices by providing an impedance detection circuitfor concurrent, co-channel radios and an RSSI based algorithm to detectRF port impedance. Aspects of the present disclosure overcome thedeficiencies of traditional wireless devices by providing a channelizedfrequency-domain reflectometry based algorithm to detect a physicaldistance to an impedance mismatch. The physical distance is between anRF port and a location where the impedance mismatch condition occurs. Atany impedance mismatch, some of the energy of an incident signal isreflected backward toward the source as a reflected signal. If thesereflections are excessive, the antenna system does not operate properly.Reflectometry is the use of radiation and reflections of radiation inthe forms of electromagnetic pulses that are used to determine alocation of an impedance mismatch condition at or beyond the RF port,such as in an RF cable coupled to the RF port. The circuitry describedherein can be placed in a reflectometry mode in order to determine aphysical distance between the RF port and the location where theimpedance mismatch condition occurs. If the antenna is disconnected, thephysical distance will be zero. If a physical attribute of the RF cableis causing the malfunction, the circuitry in the reflectometry mode candetermine the physical distance to the location causing the impedancemismatch. In time-domain reflectometry, the circuit can determine thecharacteristics of the RF cable by observing reflected waveforms. Thecharacterization can be used to locate the faults or discontinuities ina connector, in the RF cable, or the like. In frequency-domainreflectometry, the circuitry generates a sweep across a frequency range(e.g., frequencies of a channel) as an input into the transmission link.The circuitry (e.g., receiver) measures the interference patterngenerated when the swept RF source output signal adds and subtracts withreflected signals from faults and other reflective characteristicswithin the tested transmission line. The circuitry can calculate adistance to a location where the impedance mismatch condition occursbased on the measured reflected signals across the frequency range.

Aspects of the present disclosure overcome the deficiencies oftraditional wireless devices by providing a multi-mode impedancedetection circuit with RSSI and frequency-domain reflectometry modes.Aspects of the present disclosure overcome the deficiencies oftraditional wireless devices by providing airtime reservation duringRSSI detection. The aspects of the present disclosure can implement anRF port impedance detection technique that uses concurrent radios,capable of co-channel operation, to detect reflected energy from animpedance mismatch caused by a disconnected RF port or damage to an RFcable or antenna itself. The aspects of the present disclosure canimplement an impedance detection circuit, with an RF coupler, canintentionally couple the radios to enable sensing the impedance of theRF connector termination. An RSSI threshold condition, such as amismatch threshold, may be set in software based on calibrationmeasurements. In addition to an RSSI based algorithm and impedancedetection circuit to detect RF port impedance, the application alsoincludes a channelized frequency-domain reflectometry based algorithm todetect a physical distance to a location where the impedance mismatchoccurs and airtime reservation during RSSI detection. Details of thechannelized frequency-domain reflectometry based algorithm are describedbelow with respect to FIGS. 3-5 and FIG. 9 .

As described herein, concurrent radios capable of co-channel operationmay be used to detect reflected energy from an impedance mismatch suchas a disconnected RF port. Wireless devices can include wireless localarea network (WLAN) radios that operate in the 2.4 GHz and 5 GHz bandsand utilize various WLAN protocols, such as the Wi-Fi® protocols (e.g.,802.11n, 802.11ac, or the like). For example, many Wi-Fi® chipsetssupport dual concurrency on either 2.4 GHz ISM or 5 GHz U-NII bands.Typically, RF circuitry for each radio is designed to maximize isolationto avoid desensing the receivers especially for asynchronous operation(e.g., carrier-sense multiple access with collision avoidance(CSMA-CA)). However, intentional coupling between the radios enablessensing the impedance of the RF connector termination. Radio-to-radiocoupling over circuit board traces (e.g., printed circuit board (PCB)traces) may be used if the RSSI level is sufficiently high. However,there may be many coupling paths interacting in complex ways. This mayimpact the RSSI level and stability under conditions unrelated to portimpedance, including device placement relative to building structures.Therefore, in some embodiments described herein, a dedicated impedancedetection circuit is used.

Various devices are described herein that include WLAN radios operate inthe 2.4 GHz and 5 GHz frequency bands and utilize various WLANprotocols, such as the Wi-Fi® protocols (e.g., 802.11n, 802.11ac, or thelike). The radios can utilize 2×2 spatial multiplexingMultiple-input-multiple-output (MIMO) and channel bandwidths from 5 MHzto 160 MHz. The radios can see all 5.x GHz channels, including DynamicFrequency Selection (DFS) channels and can operates at an EquivalentIsotropic Radiated Power (EIRP) up to 36 dBmi, depending on the channel.Alternatively, other types of radios can be used to determine impedancemismatch conditions using the RF port impedance detection technologiesdescribed herein.

In one embodiment of dual concurrent radios, an impedancedetection-circuit includes an RF switch matrix, a bi-directional RFcoupler, and RFFE signal paths. During an impedance measurement, theRFFE circuitry is bypassed. This eliminates potential signal attenuationfrom amplifier reverse isolation. A second antenna (RX antenna) can bedisconnected from the bi-directional RF coupler to reduce unwantedleakage between RF ports. Absorptive switches (SW_A) can be used tomaintain the impedance match on coupler ports of the bi-directional RFcoupler and the RFFE circuitry. When a first radio (TX radio) transmitsa signal, the signal is reflected at the unmatched RF port (i.e. noantenna) and is routed through the bi-directional RF coupler back towarda second radio (RX radio). The second radio measures an RSSI value ofthe reflected signal. During normal radio operation, the bi-directionalRF coupler is bypassed to avoid receiver desense and reduce signal loss.An example of dual concurrent radios and an impedance detection circuitis described and illustrated below with respect to FIGS. 1A-1B. Inanother embodiment, the coupling can be done on a PCB without abi-directional coupler. Also, in other embodiments, the switch matrixcan be simplified from the illustrated embodiments.

FIG. 1A is a block diagram of a wireless device 100 with an impedancedetection circuit 102 where a first radio 106 transmits a first signalaccording to one embodiment. The wireless device 100 includes aprocessing device 104, a first radio 106, a second radio 108, and theimpedance detection circuit 102. In general, the impedance detectioncircuit 102, under control by the processing device 104, is used tomeasure one or more RSSI values of a reflected signal, the reflectedsignal being caused by an impedance mismatch condition caused by anantenna being disconnected from a first RF port (labeled as “no antenna110) or vi) damage to an RF cable coupled between the antenna and thefirst RF port (not illustrated in FIG. 1A). The RF ports are alsoreferred to as antenna ports.

In the depicted embodiment, the first radio 106 is a first WLAN radioand the second radio 108 is a second WLAN radio, both of which arecapable of co-channel operation. The first radio 106 is coupled to theprocessing device 104 and the processing device 104 can control thefirst radio 106 over a first radio control interface 101. The secondradio 108 is coupled to the processing device 104 and the processingdevice 104 can control the second radio 108 over a second radio controlinterface 103. The impedance detection circuit 102 is coupled to theprocessing device 104 and the processing device 104 can control theimpedance detection circuit 102 over a switch control interface 105.

The impedance-detector circuit 102 includes a first RF front-end (RFFE)circuitry 112, second RFFE circuitry 114, a bi-directional RF coupler116, and switching circuitry, including a first switch 118, a secondswitch 120, a third switch 122, and a fourth switch 124 in the depictedembodiment. It should be noted that other configurations of switches canbe used for the switching circuitry of the impedance detection circuit102. The bi-directional RF coupler 116 includes a first port, a secondport, a third port, and a fourth port. The switching circuitry, in acoupler mode, i) couples the first radio 106 to the first port, a firstRF port 126 to the third port, and the second radio 108 to the secondport, and ii) decouples a second RF port 128 from the fourth port. Theswitching circuitry, in a normal mode, iii) decouples the bi-directionalRF coupler 116 from each of the first radio 106, the second WLAN radio108, the first RF port 126, and the second RF port 128 and iv) couplesthe first radio 106 to the first RF port 126 via the first RFFEcircuitry 112 and the second radio 108 to the second RF port 128 via thesecond RFFE circuitry 114. The processing device 104 can receive a firstmessage from a device at a network operations center (NOC) 130. Thedevice at the NOC 130 can be a remote server that manages devices in thenetwork. The first message can include a request to check for animpedance mismatch condition caused by the first antenna beingdisconnected from the first RF port (no antenna 110) or vi) damage to anRF cable coupled between the first antenna and the first RF port 126.The processing device 104 sends a control signal over the switch controlinterface 105 to the impedance detection circuit 102 that causes theimpedance detection circuit 102 to switch from the normal mode to thecoupler mode. The processing device 104 instructs the first radio 106over the first radio control interface 101 to send a first signal viathe first RF port 126. The processing device 104 instructs the secondradio 108 over the second radio control interface 103 to measure a firstRSSI value of a first reflected signal at the second port of thebi-directional RF coupler 116. The first reflected signal 138 is causedby an impedance mismatch condition caused by the first antenna not beingcoupled to the first RF port 126 (“no antenna” 110) or damage to an RFcable coupled between the first antenna and the first RF port 126. Theprocessing device 104 determines whether the first RSSI value exceeds amismatch threshold 132. The mismatch threshold 132 represents theimpedance mismatch condition. When the RSSI value exceeds the mismatchthreshold 132, there is a high reflection between the first radio 106and the second radio 108. The high reflection causes the first reflectedsignal 138, as well as leakage at the first RF port 126. Responsive tothe processing device determining that the first RSSI value exceeds themismatch threshold 132, the processing device sends a second message tothe device at the NOC 130 (also referred to herein as a remote serverthat manages devices in a network). The second message includes aresponse with the impedance mismatch condition detected (e.g.information that identifies the first antenna not being coupled to thefirst RF port 126 (“no antenna” 110) or damage to an RF cable coupledbetween the first antenna and the first RF port 126). The processingdevice receives a third message from the device at the NOC 130, thethird message including a command to disable the first radio 106.

In one embodiment, responsive to the first RSSI value exceeding thethreshold, the processing device 104 instructs the first radio 106 tosend the same signal via the first antenna in each channel in a set ofchannels in a frequency-domain reflectometry mode. The processing device104 instructs the second radio 108 to measure a RSSI value for eachchannel in the set of channels in the frequency-domain reflectometrymode. The processing device 104 determines a physical distance betweenthe first RF port and a location where the impedance mismatch conditionoccurs using the RSSI values for the set of channels. The processingdevice 104 sends a fourth message to the device at the NOC 130. Thefourth message includes a value representing the physical distance.Alternatively, the value representing the physical distance can also bereported in the second message described above that includes anindication of the impedance mismatch condition.

The processing device 104 can include one or more Central ProcessingUnits (CPUs), microcontrollers, field programmable gate arrays, or othertypes of processors or processing devices. The processing device 104 canimplement processing logic that comprises hardware (e.g., circuitry,dedicated logic, programmable logic, microcode, etc.), software,firmware, or a combination thereof. The processing logic can configurethe wireless device 100 to operate according to any of the processesdescribed herein. The processing device 104 can communicate with otherdevices over the wired interfaces, the wireless interfaces, or anycombination thereof. The wireless device 100 can also include othercomponents, such as one or more memory devices, additional radios, wiredinterfaces, or the like.

The impedance detection circuit 102 can include the first RF port 126,the second RF port 128, a first terminal 134 coupled to the first radio106, and a second terminal 136 coupled to the second radio 108. Theswitching circuitry is coupled to the first RF port 126, the second RFport 128, the first terminal 134, the second terminal 136, and thebi-directional RF coupler 116. The processing device 104 controls theswitching circuitry to i) couple the first terminal 134 to the firstport of the bi-directional RF coupler 116, ii) couple the first RF port126 to the third port of the bi-directional RF coupler 116, iii) couplethe second terminal to the second port of the bi-directional RF coupler116, and iv) decouple the second RF port 128 from the fourth port of thebi-directional RF coupler 116. This can be done in response to theprocessing device 104 receiving a command from the NOC 130 to put theradios in a coupler mode. The processing device 104 causes the firstradio 106 to send a first signal (TX signal) via the first terminal 134.The processing device 104 causes the second radio 108 to measure a firstRSSI value of a first reflected signal 138 at the second terminal 136.The first reflected signal 138 is a reflected signal of the first signal(TX signal). The reflected signal 138 is caused by the impedancemismatch at the first RF port 110 because there is no antenna 110.Because there is no antenna 110 at the first RF port 126, there isleakage by the first radio 106. The reflected signal 138 passes from thefirst RF port 126 through the bi-directional RF coupler 116 from thethird port to the second port that is coupled to the second radio 108.The processing device 104 receives the first RSSI value from the secondradio 108 and determines that the first RSSI value exceeds the mismatchthreshold 132. The processing device sends a message indicative of theimpedance mismatch condition to a second device at the NOC 130.

In a further embodiment, the processing device 104 receives a firstmessage from a device at the NOC 130. The first message include arequest to check for an impedance mismatch condition caused by i) afirst antenna being disconnected from the first RF port 126 or ii)damage to an RF cable between the first antenna and the first RF port126. In response, the processing device sends a control signal to theswitching circuitry to switch from a normal mode to the coupler mode. Asdescribed above, in the coupler mode, the switching circuitry i) couplesthe first radio 106 to the first port of the bi-directional RF coupler116, the first RF port 126 to the third port of the bi-directional RFcoupler 116, and the second radio 108 to the second port of thebi-directional RF coupler 116, and ii) decouples the second RF port 128from the fourth port of the bi-directional RF coupler 116. In the normalmode, the switching circuitry i) decouples the bi-directional RF coupler116 from the RF paths and ii) couples the first radio 106 to the firstRF port 126 via the first RFFE circuitry 112 and the second radio 108 tothe second RF port 128 via the second RFFE circuitry 114. The switchingcircuitry decouples the bi-directional RF coupler 116 from the RF pathsby decoupling the first radio 106, the second radio 108, the first RFport 126, and the second RF port 128.

In the depicted embodiment, the switching circuitry includes the firstswitch 118 that is coupled to the first terminal 134, the first RFFEcircuitry 112, and the first port of the bi-directional RF coupler 116.The switching circuitry includes the second switch 120 that is coupledto the second terminal 136, the second RFFE circuitry 114, and thesecond port of the bi-directional RF coupler 116. The switchingcircuitry includes the third switch 122 that is coupled to the firstRFFE circuitry 112, the third port of the bi-directional RF coupler 116,and the first RF port 126. The switching circuitry includes the fourthswitch 124 that is coupled to the second RFFE circuitry 114, the fourthport of the bi-directional RF coupler 116, and the second RF port 128.The switches 118-124 can be controlled by one or more control signalsfrom the processing device 104 over the switch control interface 105.

In a further embodiment, the processing device 104 causes the secondradio 108 to send a second signal via the second terminal 136, such asillustrated and described below with respect to FIG. 1B.

FIG. 1B is the block diagram of the wireless device 100 with theimpedance detection circuit 102 where the second radio 108 transmits asecond signal according to one embodiment. The wireless device 100 inFIG. 1B is similar to the wireless device 100 in FIG. 1A, as noted bythe same reference numbers, but the second radio 108 is transmittinginstead of the first radio 106. For example, the processing device 104causes the second radio 108 to send the second signal via the secondterminal 136 and causes the first radio 106 to measure a second RSSIvalue of a second reflected signal 140 at the first terminal 116. Thesecond reflected signal 140 is a reflected signal of the second signal.The processing device 104 receives the second RSSI value from the firstradio 106 and determines whether the second RSSI value exceeds themismatch threshold 132. The mismatch threshold 132 represents theimpedance mismatch condition. In this case, the processing device 104determines that the second RSSI value does not exceed the mismatchthreshold 132. When the RSSI value does not exceed the mismatchthreshold 132, there is a low reflection between the first radio 106 andthe second radio 108. The low reflection is caused because a secondantenna 142 is coupled to the second RF port 128 and is well matched.The second antenna 142 may not be perfectly matched, so there can stillbe the second reflected signal 140 that passes from the second RF port128 through the bidirectional RF coupler 116 from the fourth port to thefirst port that is coupled to the first radio 106. The matched antennaload with low reflection causes efficient radiation by the secondantenna 142. The matched antenna load with low reflection causes thesecond reflected signal 140 to be lower than the first reflected signal138, as well as lower than the mismatch threshold 132. The processingdevice 104 receives the second RSSI value from the first radio 106 anddetermines that the second RSSI value does not exceed the mismatchthreshold 132. In one embodiment, the processing device 104 sends amessage with an indication that there is not an impedance mismatchcondition at the second RF port 128. In another embodiment, theprocessing device 104 determines the impedance mismatch condition whenthe first RSSI value exceeds the mismatch threshold 132 and the secondRSSI value does not exceed the mismatch threshold 132. That is, theprocessing device 104 can send the indication of the impedance mismatchcondition to the second device at the NOC 130 responsive to the firstRSSI value exceeding the threshold and the second RSSI value notexceeding the threshold. As described above, the impedance mismatchcondition is caused by i) a first antenna being disconnected from thefirst RF port 126 (i.e., no antenna 110) or ii) a physical attribute ofan RF cable that is coupled between the first antenna and the first RFport 126. The physical attribute can be a damaged portion of the RFcable, poor shielding, or the like.

It should be noted that there is very little reflected energy coupled tothe first radio 106 when the second radio 108 is properly impedancematched by the second antenna 140, as shown in FIG. 1B. The differencein RSSI between matched and mismatched can be set to be in the tens ofdB at the receiving radio. An RSSI threshold condition may be set insoftware based on calibration measurements at the factory.

As illustrated in FIGS. 1A-1B, the impedance detection circuit 102 canbe used to detect an impedance mismatch condition using the two radios:first radio 106 and second radio 108. In other embodiments, the wirelessdevice 100 includes one or more additional radios and the switchingcircuitry of the impedance detection circuit 102 can connect thebi-directional RF coupler 116 between any pair of the three or moreradios. Alternatively, the processing device 104 can control theswitching circuitry in other manners to transmit a signal and measure anRSSI value at each of the other radios, for example.

The technology described above with respect to two antennas can beimplemented to devices with more than two concurrent radios. In oneembodiment, each pair of radios uses the same impedance detectioncircuit described above. In another embodiment, all radios can becoupled through a Butler matrix, as described below. In a four-radioexample, such as illustrated in FIG. 2 , a single RF port is routed tothe Butler matrix using an RF switch. All other RF ports aredisconnected from the Butler matrix. Cascaded hybrid couplers are usedto distribute the reflected signals to all radios in receive mode. Eachradio can receive a similar RSSI level, which can be compared, averaged,or otherwise processed in parallel to determine whether there is animpedance mismatch condition at an RF port.

In one embodiment, the processing device 104 controls the first radio106 to be coupled to the first terminal 134 during a first time periodand during a second time period. The processing device 104 controls thesecond radio 108 to be coupled to the second terminal 136 during thefirst time period and a third radio (not illustrated in FIGS. 1A-1B) tobe coupled to the second terminal 136 during the second time period.During the first time period, the processing device 104 causes the firstradio to send a third signal and causes the second radio to measure athird RSSI value of a third reflected signal at the second terminal 136.During the second time period, the processing device 104 causes thefirst radio to send a fourth signal and causes the third radio tomeasure a fourth RSSI value of a fourth reflected signal at the secondterminal 136. The processing device 104 receives the third RSSI valuefrom the second radio and the fourth RSSI value from the third radio.The processing device 104 determines whether the third RSSI value or thefourth RSSI value exceed the mismatch threshold 132. The processingdevice sends one or more indications of any impedance mismatchconditions to the device at the NOC 130. For example, the impedancemismatch condition is caused by a first antenna not being connected tothe first RF port 126 or damage to the RF cable. Alternatively, theimpedance mismatch condition can be caused by a second antenna not beingconnected to the second RF port 128. In another embodiment, the firstradio sends the third signal and both the second radio and the thirdradio each receive a reflected signal and each measure a RSSI value.

In another embodiment, the first radio is coupled to the first terminalduring a first time period, the second radio is coupled to the secondterminal during the first time period, a third radio is coupled to thefirst terminal during a second time period, and a fourth radio iscoupled to the second terminal during the second time period. Theprocessing device 104, during the first time period, causes the firstradio to send the first signal and causes the second radio to measurethe first RSSI value. The processing device 104, during the second timeperiod, causes the third radio to send a second signal and causes thefourth radio to measure a second RSSI value of a second reflected signalat the second terminal. The processing device 104 receives the secondRSSI value from the fourth radio and determines that the second RSSIvalue exceeds the mismatch threshold. The processing device sends asecond indication of a second impedance mismatch condition to the seconddevice responsive to the second RSSI value exceeding the threshold. Theimpedance mismatch condition can be caused by i) a first antenna beingdisconnected from the first RF port during the first time period or ii)damage to an RF cable that is coupled between the first antenna and thefirst RF port during the first time period. In this embodiment, thesecond antenna is connected to the second RF port during the first timeperiod. The second impedance mismatch condition can be caused by i) athird antenna being disconnected from the first RF port during thesecond time period or ii) damage to a second RF cable that is coupledbetween the third antenna and the first RF port during the second timeperiod. In this case, a fourth antenna is connected to the second RFport during the second time period.

In another embodiment, the switching circuitry includes a butler matrix,such as illustrated and described with respect to FIG. 2 .

FIG. 2 is a block diagram of a wireless device 200 with an impedancedetection circuit 202 with a butler matrix according to one embodiment.The wireless device 200 includes a processing device 204, a first radio206, a second radio 208, a third radio 246, a fourth radio 248, and theimpedance detection circuit 202. In general, the impedance detectioncircuit 202, under control by the processing device 204, is used tomeasure one or more RSSI values of one or more reflected signals, thereflected signals being caused by an impedance mismatch condition causedby an antenna being disconnected from a first RF port 226 (labeled as“no antenna 210) or vi) damage to an RF cable coupled between theantenna and the first RF port 226 (not illustrated in FIG. 2 ).

In the depicted embodiment, the first radio 206 is a first WLAN radio,the second radio 208 is a second WLAN radio, the third radio 246 is athird WLAN radio, and the fourth radio 248 is a fourth WLAN radio, eachof which is capable of co-channel operation. The first radio 206 iscoupled to the processing device 204 and the processing device 204 cancontrol the first radio 206 over a first radio control interface 201.The second radio 208 is coupled to the processing device 204 and theprocessing device 204 can control the second radio 208 over a secondradio control interface 203. The third radio 246 is coupled to theprocessing device 204 and the processing device 204 can control thethird radio 246 over a third radio control interface 207. The fourthradio 248 is coupled to the processing device 204 and the processingdevice 204 can control the fourth radio 248 over a fourth radio controlinterface 209. The impedance detection circuit 202 is coupled to theprocessing device 204 and the processing device 204 can control theimpedance detection circuit 202 over a switch control interface 205. Theimpedance-detector circuit 202 includes a first RFFE circuitry 212,second RFFE circuitry 214, third RFFE circuitry 252, fourth RFFEcircuitry 254, the butler matrix, and switching circuitry, including afirst switch 218, a second switch 220, a third switch 222, a fourthswitch 224, a fifth switch 258 coupled to a third terminal 274, a sixthswitch 260 coupled to a fourth terminal 276, a seventh switch 262coupled to a third RF port 266, and an eighth switch 264 coupled to afourth RF port 268, as set forth in the depicted embodiment. Theswitches 218-224 and 258-264 can be controlled by one or more controlsignals from the processing device 204 over the switch control interface205. It should be noted that other configurations of switches can beused for the switching circuitry of the impedance detection circuit 202.

As illustrated in the depicted embodiment, the butler matrix includes: ai) bi-directional RF coupler 216 that includes a first port, a secondport, a third port, and a fourth port; ii) a second bi-directional RFcoupler 256 that includes a first port, a second port, a third port, anda fourth port; iii) a first phase shifter 217; iv) a second phaseshifter 257; v) a third bi-directional RF coupler 219; and vi) a fourthbi-directional RF coupler 259.

In one embodiment, the switching circuitry, in a coupler mode, i)couples the first radio 206 to the first port of the firstbi-directional RF coupler 216 via the first switch 218, a first RF port226 to the third port of the first bi-directional RF coupler 216 via thefirst phase shifter 217, the third bi-directional RF coupler 219, andthe second switch 222. In the coupler mode, the switching circuitry alsoii) couples the second radio 2018 to the second port of the firstbi-directional RF coupler 216 via the second switch 220, and the secondradio 208 to the second port, and iii) decouples a second RF port 228from the fourth port of the third bi-directional RF coupler 219. Thefourth port of the first bi-directional RF coupler 216 is coupled to afirst port of the fourth bi-directional RF coupler 259. A third port ofthe second bi-directional RF coupler 256 is coupled to a second port ofthe third bi-directional RF coupler 219. In the coupler mode, theswitching circuitry also iv) couples the third radio 246 to the firstport of the second bi-directional RF coupler 256 via the fifth switch258. The switching circuitry also v) decouples a third RF port 266 fromthe second port of the fourth bi-directional RF coupler 259 and a fourthRF port 268 from a fourth port of the fourth bi-directional RF coupler259.

The switching circuitry, in a normal mode, i) decouples the firstbi-directional RF coupler 216, the second bi-directional RF coupler 256,the third bi-directional RF coupler 219, and the fourth bi-directionalRF coupler 259 from each of the radios and each of the RF ports; and ii)couples each of the respective RFFE circuitry 212, 214, 252, and 254 toeach of the radios 206, 208, 246, and 248, respectively and to each ofthe RF ports 226, 228, 266, and 268, respectively.

In the normal mode, the processing device 204 can receive a firstmessage from a device at a NOC 230. The first message can include arequest to check for an impedance mismatch condition caused by the firstantenna being disconnected from the first RF port (no antenna 210) orvi) damage to an RF cable coupled between the first antenna and thefirst RF port 226. The processing device 204 sends a control signal overthe switch control interface 205 to the impedance detection circuit 202that causes the impedance detection circuit 202 to switch from thenormal mode to the coupler mode as set forth above. The processingdevice 204 instructs the first radio 206 over the first radio controlinterface 201 to send a first signal via the first RF port 226. Theprocessing device 204 instructs the second radio 208 over the secondradio control interface 203 to measure a first RSSI value of a firstreflected signal 238 at the second port of the first bi-directional RFcoupler 216. The processing device 204 instructs the third radio 246over the third radio control interface 207 to measure a second RSSIvalue of a second reflected signal 278 at the first port of the secondbi-directional RF coupler 256. The processing device 204 instructs thefourth radio 248 over the fourth radio control interface 209 to measurea third RSSI value of a third reflected signal 282 at the second port ofthe second bi-directional RF coupler 256. The first reflected signal238, the second reflected signal 278, and the third reflected signal 282are caused by an impedance mismatch condition caused by the firstantenna not being coupled to the first RF port 226 (“no antenna” 210) ordamage to an RF cable coupled between the first antenna and the first RFport 226.

The processing device 204 receives the first RSSI value from the secondradio 208, the second RSSI value from the third radio 246, and the thirdRSSI value from the fourth radio 248. The processing device 204determines whether each of the first, second, and third RSSI valuesexceed a mismatch threshold 232. The mismatch threshold 232 representsthe impedance mismatch condition. When an RSSI value exceeds themismatch threshold 232, there is a high reflection between the receivingradio and the transmitting radio. The high reflection causes thereflected signals, as well as leakage at the first RF port 226.Responsive to the processing device determining that one or more of theRSSI values exceed the mismatch threshold 232, the processing device 204sends a second message to the device at the NOC 230. The second messageincludes a response with the impedance mismatch condition detected (e.g.information that identifies the first antenna not being coupled to thefirst RF port 226 (“no antenna” 210) or damage to an RF cable coupledbetween the first antenna and the first RF port 226).

In other embodiments, the processing device 204 can controltransmissions by the first radio 206 over a set of channels in afrequency-domain reflectometry mode. In the frequency-domainreflectometry mode, the processing device can determine a physicaldistance of the mismatch impedance condition using the RSSI values overthe set of channels. As described herein, the physical distance isbetween an RF port 226 and a location 225 where the impedance mismatchcondition occurs. The processing device 204 can receive a command thatinstructs the processing device 204 to enter the frequency-domainreflectometry mode after determining that an impedance mismatchcondition is detected. In the frequency-domain reflectometry mode, theprocessing device 204 can perform a channel sweep and measure RSSImeasurements of the reflected signals during the channel sweep. Theprocessing device computes a reflection distance using the RSSImeasurements, such as illustrated in FIG. 5 , the reflection distancebeing between the RF port and a location where the impedance mismatchcondition occurs. The processing device 204 sends a third message to thedevice at the NOC 230. The third message includes the physical distanceof the impedance mismatch condition. The physical distance can also bereported in the second message described above that includes theimpedance mismatch condition.

Like the processing device 104, the processing device 204 can includeone or more CPUs, microcontrollers, field programmable gate arrays, orother types of processors or processing devices. The processing device204 can implement processing logic that comprises hardware (e.g.,circuitry, dedicated logic, programmable logic, microcode, etc.),software, firmware, or a combination thereof. The processing logic canconfigure the wireless device 200 to operate according to any of theprocesses described herein. The processing device 204 can communicatewith other devices over the wired interfaces, the wireless interfaces,or any combination thereof. The wireless device 200 can also includeother components, such as one or more memory devices, additional radios,wired interfaces, or the like.

In other embodiments, the processing device 204 can check each of theother RF ports 228, 266, and 268 in a similar fashion as the first RFport 226 as described above. In those embodiments, the processing device204 sends different control signals to the respective radios to transmitand receive and measure the RSSI values of the reflected signals. Theprocessing device 204 determines whether the impedance mismatchconditions occur on the respective RF port using the measured RSSIvalues. Similarly, the processing device 204 can determine a physicaldistance in the frequency-domain reflectometry modes for each of the RFports.

In one embodiment, the switching circuitry of the impedance detectioncircuit 202 includes: the first switch 218 that is coupled to the firstterminal 234, the first RFFE circuitry 212 and the first port of thefirst bi-directional RF coupler 216; the second switch 220 that iscoupled to the second terminal 236, the second RFFE circuitry 214 andthe second port of the first bi-directional RF coupler 212; the thirdswitch 222 that is coupled to the first RFFE circuit 212, the first RFport 226, and a third port of the third bi-directional RF coupler 219, afirst port of the third bi-directional RF coupler 219 being coupled to asecond port of the first bi-directional RF coupler 216 via a first phaseshifter 217; the fourth switch 224 that is coupled to a fourth port ofthe second bi-directional RF coupler 256, the second RF port 228, andthe second RFFE circuitry 214; the fifth switch 258 that is coupled to athird terminal 274, the third RFFE circuitry 252, and a first port ofthe second bi-directional RF coupler 256; the sixth switch 260 that iscoupled to a fourth terminal 276, a fourth RFFE circuitry 254, and asecond port of the second bi-directional RF coupler 256, a third port ofthe second bi-directional RF coupler 256 being coupled to a second portof the third bi-directional RF coupler 219; the seventh switch 262 thatis coupled to the third RFFE circuitry 252, a third RF port 266, and asecond port of a fourth bi-directional RF coupler 259, a first port ofthe fourth bi-directional RF coupler 259 being coupled to a fourth portof the first bi-directional RF coupler 216 and a second port of thefourth bi-directional RF coupler 259 being coupled to a fourth port ofthe second bi-directional RF coupler 256 via a second phase shifter 257;and the eighth switch 265 that is coupled to a fourth port of the fourthbi-directional RF coupler 259, a fourth RF port 268, and the fourth RFFEcircuitry 254. The processing device 204 can control the switchingcircuitry to be in this configuration for a coupled mode. The processingdevice 204 can control the switching circuitry to switch between anormal mode and the coupled mode. In the normal mode, each of therespective RFFE circuitry is switched between a terminal and an RF port,removing the bi-directional RF couplers and the phase shifters out ofthe RF paths.

In a first mode, the processing device 204 can determine RSSI values andan impedance mismatch condition using a RSSI-based impedance detectionalgorithm. In a second mode (e.g., frequency-domain reflectometry mode),the processing device can determine RSSI values and a physical distanceof the impedance mismatch condition using a RSSI-based frequency-domainreflectometry algorithm. In the second mode, the processing device 204can cause the first radio 206 to i) send a set of signals, including thefirst signal, and ii) cause the second radio to measure a first set ofRSSI values, including the first RSSI value, the third radio to measurea second set of RSSI values, and the fourth radio to measure a third setof RSSI values, wherein each of the set of signals has a differentfrequency of a channel. Each of the first set of RSSI values correspondsto each of the different frequencies of the channel. Each of the secondset of RSSI values corresponds to each of the different frequencies ofthe channel. Each of the third set of RSSI values corresponds to each ofthe different frequencies of the channel. The processing device 204determines a reflection distance to a location where the impedancemismatch condition occurs, such as at or beyond the first RF port, usingthe first set of RSSI values, the second set of RSSI values, and thethird set of RSSI values. The processing device sends a valuerepresenting the reflection distance to the second device at the NOC230.

As described herein, the impedance detection circuit can operate as afrequency domain reflectometer (also referred to herein as operating ina “frequency domain reflectometry” mode). The RSSI level can be used todetermine the level of reflected energy from a particular RF port.However, this information alone does not indicate a physical distance(e.g., a location) of the impedance mismatch. For example, the impedancemismatch condition may actually be due to reflections from scatterersnear an antenna, such as illustrated in FIG. 3 . A nearby scatterer is anearby object that refracts or diffracts electromagnetic radiationirregularly to diffuse in many directions. Once the physical distance isdetermined by the wireless device in the frequency domain reflectometrymode, the wireless device can send this information to the NOC. Thereare circumstances where it will be useful at the NOC to know if signaldegradation is occurring at the RF ports or beyond the antenna.

FIG. 3 is a block diagram of the wireless device 100 with the impedancedetection circuit 102 in a frequency domain reflectometry mode accordingto one embodiment. The wireless device 100 is similar to the wirelessdevice 100 described above with respect to FIGS. 1A-1B, as noted bysimilar components with the same reference numbers. In the frequencydomain reflectometry mode, the processing device 104 can measure RSSIvalues of reflected signals due to a nearby scatter 310. As illustratedin FIG. 3 , the first radio 134 can measure a signal 338 that passesthrough the bi-directional RF coupler 116 from the second RF port 128.The signal 338 can be representative of reflection caused by the nearbyscatterer 310. The RSSI values measured in the frequency domainreflectometry mode can be used to determine a physical location of theimpedance mismatch condition from frequency spacing between reflectionnulls. The coupler-based frequency domain reflectometer shown in FIG. 3can rely on constructive and destructive interference between reflectedand coupled signals, such as illustrated and described below withrespect to FIG. 4

FIG. 4 illustrates operation of a bi-directional RF coupler 400 in afrequency domain reflectometry mode according to one embodiment. Thebi-directional RF coupler 400 in the frequency domain is similar to thebi-directional RF couplers described herein, such as the bi-directionalRF coupler 102 of FIGS. 1A-1B. The bi-directional RF coupler 400 relieson constructive and destructive interference between reflected andcoupled signals. An incident transmitted signal 401, at a first inputport 402, is coupled to an unmatched coupler port (CPL) 404 and is usedas a reflectometer reference signal 403. The open circuit impedancemismatch reflects a reflected signal 405 through the bi-directional RFcoupler 400 to a test port 406 (TEST). A reference signal level 407 isequal to the transmit power of the incident transmitted signal 401 minusa coupling coefficient (i.e. 10 dB coupler) and insertion losses. Theincident-transmitted signal 401 is routed through the bi-directionalcoupler 400 to an antenna port 408 as a test signal 409. Depending onantenna port impedance, some of the test signal 409 is reflected backtoward the bi-directional RF coupler 400 as a reflected test signal 411.The reflected test signal 411 is then coupled to the test port 406 as atest signal 413 and combined with the reference signal 407. Thisproduces frequency domain nulls whenever the test signal 413 andreference signal 407 are out of phase by 180 degrees (180°), asillustrated in FIG. 5 .

As described herein, the bi-directional RF coupler 400 in a frequencydomain reflectometry mode can determine a reflection distance 415between the RF port 408 and a location 417 where the impedance mismatchcondition occurs. Here, the impedance mismatch condition occurs atlocation 417 because of a disconnected antenna port. In other cases, thelocation 417 could be at other locations along the transmission line (RFcabling 410) between the RF port 408 and the antenna port due to somephysical attribute that causes malfunction of the RF cabling 410.

FIG. 5 illustrates a frequency domain reflectometer visualization 500 ofthe bi-directional RF coupler 400 of FIG. 4 according to one embodiment.The test signal 413 accumulates phase as it propagates along RF cabling410 in both forward (incident) and reverse directions (reflection). Forsimplicity, assume the phase of the reference signal 407 at the testport 406 is 0°. Nulls will occur when the phase difference equals an oddmultiple of 180° as set forth in equation (1):φ_(n)=φ_(t)−φ_(r)=(2n−1)π−,  (1)where φ_(t) is the test signal phase, φ_(r)=0° is the reference signalphase and n=1,2,3, . . . .

The phase difference in terms of propagation coefficient and distanceare set forth in equations (2) and (3):

$\begin{matrix}{\beta_{n} = \frac{4\pi f_{n}}{v_{p}}} & (2)\end{matrix}$ $\begin{matrix}{\varphi_{n} = {{2\beta_{n}R} = {\left( {{2n} - 1} \right)\pi}}} & (3)\end{matrix}$

Differentiating with respect to n and solving for distance R gives thesimple relation between null spacing and distance to impedance mismatch,as set forth in equation (4):

$\begin{matrix}{R = \frac{v_{p}}{\left( {2{\pi\Delta}f} \right)}} & (4)\end{matrix}$where v_(p) is the phase velocity of the transmission line.

Minimum distance resolution for this reflectometer type is expressed inequation (5):

$\begin{matrix}{{\Delta{R(m)}} = {\left( {{1.5} \times 10^{8}} \right)\frac{v_{p}}{BW}}} & (5)\end{matrix}$where v_(p) is the phase velocity of the transmission line and the BW isthe total bandwidth available.

The maximum detectable range is expressed in equation (6):R(m)=N×ΔR  (6)where N is the number of sample points within the available bandwidth.

For example, consider the approximate frequency spectrum (e.g., ˜600MHz) in the 5.170 to 5.825 GHz U-NII band. Assuming a phase velocity,v_(p)=0.7, the minimum detectable distance is ≈0.2 m. Maximum distancedetection is ≈20 m when measured on approximately one-hundred 5 MHzchannels. The difference between disconnected antenna (<5 m) and nearbyreflections (>5 m) are both detectable within this range.

FIG. 6A is a graph 600 of S-parameter measurements for a bi-directionalcoupler according to one embodiment. The graph 600 shows the measurednull spacing for different unterminated antenna port cable lengths. Forexample, a 2-meter cable sample has 50 MHz null spacing. This resultscales to the predicted 20 meters maximum cable length when measuredusing 5 MHz channels. One interesting observation is that the nulldepths decrease as cable length increases. This is because the reflectedtest signal amplitude reduces as the cable loss increases. The referencesignal remains unchanged resulting in partial signal cancellation at thetest port. One method to improve the null depth is to match the test andreference signal amplitudes using an attenuator at the coupler (CPL)port. A 5 dB improvement in null depth is shown in FIG. 6B.

FIG. 6B is a graph 650 of S-parameter measurements for a bi-directionalcoupler with an attenuator at a coupler (CPL) port according to oneembodiment. The graph 650 shows the null depth dependence on CPL portimpedance load.

In addition to operating as a frequency domain reflectometer, theimpedance detection circuit can be used in a multi-mode port impedancecircuit, as described and illustrated below with respect to FIGS. 7-8 .RSSI and reflectometer functionality require different CPL portterminations. For example, RSSI level measurements have flat frequencyresponse and highest accuracy when CPL port is match terminated. Incontrast, reflectometry is best suited with a reflective (open or shortcircuit) or partial attenuation at the CPL port. Therefore, a modifiedimpedance detection circuit may be used. In this embodiment, a pair ofreflective RF switches (SW_R) is added to the impedance detectioncircuit as shown and described below with respect to FIG. 7 and FIG. 8 .This allows the CPL port to be switched between RSSI (matched CPL load)and reflectometry (reflective or partially attenuated CPL load).

FIG. 7 is a block diagram of a wireless device 700 with an impedancedetection circuit 702 with a pair of reflective RF switches (SW_R) 722,724 in an RSSI mode according to one embodiment. The wireless device 700is similar to the wireless device 700 described above with respect toFIGS. 1A-1B, as noted by similar components with the same referencenumbers. The impedance detection circuit 702 is similar to the impedancedetection circuit 102 described above with respect to FIGS. 1A-1B, asnoted by similar components with the same reference numbers. In the RSSImode, the processing device 104 controls the pair of reflective RFswitch 722, 724. In particular, the processing device 104 connects thereflective switch 722 between the second port of the bi-directional RFcoupler 116 and the third switch 122, which is coupled to the first RFport 126. The processing device 104 connects the reflective switch 724between the fourth port of the bi-directional RF coupler 116 and thefourth switch 124, which is coupled to the second RF port 126. Thereflective switch 724 is coupled to a matched port 726, causing amatched CPL load on the bi-directional RF coupler 116.

FIG. 8 is a block diagram of the wireless device 700 with the impedancedetection circuit 702 with a pair of reflective RF switches (SW_R) in areflectometry mode according to one embodiment. In the frequency domainreflectometry mode, the processing device 104 connects the reflectiveswitch 722 between the second port of the bi-directional RF coupler 116and the third switch 122, which is coupled to the first RF port 126. Theprocessing device 104 connects the reflective switch 724 between thefourth port of the bi-directional RF coupler 116 and the fourth switch124, which is coupled to the second RF port 126. The reflective switch724 is coupled to a reflective/attenuated port 826, causing a reflectiveor partially attenuated CPL load CPL load on the bi-directional RFcoupler 116.

FIG. 9 is a flow diagram of a method 900 of determining a reflectiondistance of an impedance mismatch condition according to one embodiment.The method 900 may be performed by processing logic that compriseshardware (e.g., circuitry, dedicated logic, programmable logic,microcode, etc.), software, firmware, or a combination thereof. In oneembodiment, the method 900 may be performed by any of the processingdevice devices described herein and illustrated with respect to FIGS.1-8 .

Referring back to FIG. 9 , the method 900 begins by the processing logicreceiving a first message from a second device, such as a device 901 ata NOC, the first message including a request to check for an impedancemismatch condition caused by i) a first antenna being disconnected froma first RF port of the wireless device or ii) damage to an RF cablecoupled between the first antenna and the first RF port, and areflection distance to a location where the impedance mismatch conditionoccurs (block 902). The processing logic determines whether a reflectedsignal is detected (block 904). The reflected signal can be whetherthere RSSI values at the second radio are measured. If there is noreflected signal, the processing logic can transition to a normal radiooperation (block 906). If there are RSSI values for the reflectedsignal, the processing logic can instruct the first radio to be in atransmit (TX) mode (block 908) and the second radio to be in a receive(RX) mode (block 910). The first radio transmits an RF signal in the TXmode and the second radio receives a reflected signal in the RX mode.The processing logic also instructs the switching circuitry to switchinto a coupler mode (block 912). The processing logic receives RSSImeasurement(s) (e.g., RSSI values) from the second radio (block 914).The processing logic determines whether the RSSI measurement(s) exceed amismatch threshold corresponding to an impedance mismatch condition(block 916). If the RSSI measurement(s) do not exceed the mismatchthreshold at block 916, the processing logic can transition to thenormal radio operation at block 906. If the RSSI measurement(s) exceedthe mismatch threshold at block 918, the processing logic can transitionfrom an RSSI mode to a reflectometry mode in which the processing logicperforms a channel sweep using the first radio (block 918). Theprocessing device receives RSSI measurement(s) from the second radio(block 920). The processing logic determines whether additional channelsstill need to be swept (block 922). If more channels need to be swept,the processing logic returns to block 918. If the channel sweep is doneon the last channel at block 922, the processing logic computes areflection distance of the impedance mismatch condition (block 924), andthe processing logic sends the impedance mismatch condition and thereflection distance back to the device 901 at the NOC (block 926); andthe method 900 ends.

FIG. 10 is a flow diagram of a method 1000 of determining an impedancemismatch condition according to one embodiment. The method 1000 may beperformed by processing logic that comprises hardware (e.g., circuitry,dedicated logic, programmable logic, microcode, etc.), software,firmware, or a combination thereof. In one embodiment, the method 1000may be performed by any of the processing device devices describedherein and illustrated with respect to FIGS. 1-8 .

Referring back to FIG. 10 , the method 1000 begins by the processinglogic receiving a first message from a second device (block 1002). Thefirst message comprises a request to check for an impedance mismatchcondition caused by i) a first antenna being disconnected from a firstRF port of the wireless device or ii) damage to an RF cable coupledbetween the first antenna and the first RF port. The processing logiccouples a first radio to a first port of a coupler of the wirelessdevice (block 1004). The processing logic couples a second radio to asecond port of the coupler (block 1006). The processing logic couples afirst RF port to a third port of the coupler (block 1008). Theprocessing logic decouples a second RF port from a fourth port of thecoupler (block 1010). The processing logic causes the first radio tosend a first signal via the first terminal (block 1012). The processinglogic causes the second radio to measure a first RSSI value of a firstreflected signal at the second terminal (block 1014). The processinglogic receives the first RSSI value from the second radio (block 1016)and determines that the first RSSI value exceeds a threshold (block1018). The threshold represents an impedance mismatch condition at orbeyond the first RF port. The processing logic sends a response to thesecond device (block 1020), the response including an indication of theimpedance mismatch condition; and the method 1000 ends.

In a further embodiment, the first message includes a scheduled time forthe check. The processing logic sets the first radio to operate in a TXmode and the second radio to operate in a receive (RX) mode responsiveto the scheduled time. The processing logic sets the switching circuitryto operate in a coupler mode in which the switching circuitry is to i)couple the first radio to the first port, ii) couple the second radio tothe second port, iii) couple the first RF port to the third port, andiv) decouple the second antenna from the fourth port. The processinglogic causes the first radio to send the first signal and causes thesecond radio to measure the first RSSI value while the switchingcircuitry is set to operate in the coupler mode. In another embodiment,the processing logic sets the switching circuitry to operate in a normalradio mode. In the normal radio mode, the switching circuitry decouplesthe first radio from the first port, decouples the second radio from thesecond port, decouples the first RF port from the third port, andcouples the first radio to the first RF port and the second radio to thesecond RF port. This bypasses the coupler.

In another embodiment, the processing logic causes the first radio tosend a set of signals in a channel sweep. Each signal in the set ofsignals has a different frequency in the channel. The processing logiccauses the second radio to measure a set of RSSI values, each of the setof RSSI values corresponding to a reflected signal associated with eachof the set of signals. The processing logic determines a reflectiondistance to a location where the impedance mismatch condition occursusing the set of RSSI values. The processing logic sends the reflectiondistance to the second device.

In another embodiment, the processing logic causes the second radio tosend a second signal via the second terminal. The processing logiccauses the first radio to measure a second RSSI value of a secondreflected signal at the first terminal. The processing logic receivesthe second RSSI value from the first radio. The processing logicdetermines that the second RSSI value does not exceed the threshold. Theprocessing logic can send the indication responsive to the first RSSIvalue exceeding the threshold and the second RSSI value not exceedingthe threshold. In another embodiment, the processing logic determinesthat the second RSSI value does exceed the threshold. The processinglogic can send the indication responsive to the first RSSI value and thesecond RSSI value exceeding the threshold.

In another embodiment, the coupling of the first radio to the firstport, the coupling of second radio to the second port, and the couplingof first RF port to the third port, and the decoupling the second RFport from the fourth port are performed during a first time period.During a second time period that is different than the first period, theprocessing logic: couples a third radio to the first port; couples afourth radio to the second port; couples a third RF port to the thirdport; and decouples a fourth RF port from the fourth port. Theprocessing logic causes the third radio to send a second signal andcauses the fourth radio to measure a second RSSI value of a secondreflected signal at the second terminal. The processing logic receivesthe second RSSI value from the fourth radio and determines that thesecond RSSI value exceeds the threshold. The processing logic sends asecond indication of a second impedance mismatch condition to the seconddevice responsive to the second RSSI value exceeding the threshold. Thesecond impedance mismatch condition can be caused by i) a third antennabeing disconnected from the third RF port during the second time periodor ii) damage to a second RF cable that is coupled between the thirdantenna and the third RF port during the second time period. It shouldbe noted that a second antenna is connected to the second RF port duringthe first time period and a fourth antenna is connected to the fourth RFport during the second time period.

In another embodiment, the processing logic causes the first radio tosend a frame that reserves a channel for a duration of time. Theprocessing logic causes the first radio to send the first signal as adata frame after sending the frame. The data frame includes adestination address set to an address of the wireless device itself. Theprocessing logic causes the second radio measure the first RSSI valueduring the duration of time.

In one embodiment, to perform an accurate RSSI measurement, the wirelessdevice can transmit a clear to send to self (CTS-to-Self) frame toreserve a wireless medium for up to a duration of time (e.g., 32milliseconds) that the RSSI measurement is taking place. After theCTS-to-Self frame, the wireless device sends a data frame (e.g.,1500-byte data frame) with a destination address set as itself and usesthe data frame for the impedance detection, such as illustrated in FIG.11 .

FIG. 11 is a timing diagram 1000 illustrating a wireless devicetransmitting a first frame 1102 to reserve a medium (e.g., a channel)and a data frame for impedance detection according to one embodiment.The processing device causes the first radio to send a first frame 1102(e.g., CTS-to-self) that reserves a wireless medium for a duration oftime 1104. The processing device sends a second frame 1106 (e.g., dataframe) with a destination address set to an address of the wirelessdevice. The processing device causes the second radio to measure a RSSIvalue during the duration of time 1104 (also referred to as thedetection period 1104).

In one embodiment, the first frame 1102 can be sent after an idletimeout period 1108 that follows normal traffic 1110 during a serviceperiod 1112. The idle timeout period 1108 occurs during a silent period1114. After the detection period 1104, normal traffic 1116 can resumeduring a service period 1118.

The embodiments described herein include an RSSI based algorithm todetect RF port impedance. The embodiments described herein can include achannelized frequency domain reflectometry based algorithm to detect aphysical distance to impedance mismatch. The embodiments describedherein can include a dedicated RSSI based impedance detection circuitfor concurrent, co-channel radios. The embodiments described herein caninclude a multi-mode impedance detection circuit with a RSSI mode and afrequency domain reflectometry mode. The embodiments described hereincan include an airtime reservation during RSSI detection. Alternatively,any combination of these features can be used together.

FIG. 12 is a block diagram of an electronic device 1200 that can beconfigured to detect an impedance mismatch condition and a physicaldistance to a location where the impedance mismatch condition occurs asdescribed herein according to one embodiment. The electronic device 1200may correspond to the electronic devices described above with respect toFIGS. 1-11 . In one embodiment, the electronic device 1200 is thewireless devices described herein and includes an impedance detectioncircuit 1201. The impedance detection circuit 1201 can be the impedancedetection circuit 102 of FIGS. 1A, 1B, 3 , the impedance detectioncircuit 202 of FIG. 2 , or the impedance detection circuit 702 of FIG.7, 8 . Alternatively, the electronic device 1200 is coupled to theimpedance detection circuit 1201. The impedance detection circuit 1201can be the impedance detection circuit 102 of FIGS. 1A, 1B, 3 , theimpedance detection circuit 202 of FIG. 2 , or the impedance detectioncircuit 702 of FIG. 7, 8 . Alternatively, the electronic device 1200 maybe other electronic devices, as described herein.

The electronic device 1200 includes one or more processor(s) 1230, suchas one or more CPUs, microcontrollers, field programmable gate arrays,or other types of processors. The electronic device 1200 also includessystem memory 1206, which may correspond to any combination of volatileand/or non-volatile storage mechanisms. The system memory 1206 storesinformation that provides operating system component 1208, variousprogram modules 1210, program data 1212, and/or other components. In oneembodiment, the system memory 1206 stores instructions of methods tocontrol operation of the electronic device 1200. The electronic device1200 performs functions by using the processor(s) 1230 to executeinstructions provided by the system memory 1206. In one embodiment, theprogram modules 1210 may include RSSI based impedance detection logic1203 and RSSI based reflectometry logic 1205 that may perform some orall of the operations described herein, such as the method 900, themethod 1000, or any combination thereof. The RSSI based impedancedetection logic 1203 may perform some or all of the operations describedherein to detect an impedance mismatch condition. The RSSI basedreflectometry logic 1205 may perform some or all of the operationsdescribed herein to determine a physical distance to a location wherethe impedance mismatch condition occurs.

The electronic device 1200 also includes a data storage device 1214 thatmay be composed of one or more types of removable storage and/or one ormore types of non-removable storage. The data storage device 1214includes a computer-readable storage medium 1216 on which is stored oneor more sets of instructions embodying any of the methodologies orfunctions described herein. Instructions for the program modules 1210(e.g., RSSI based impedance detection logic 1203 and RSSI basedreflectometry logic 1205) may reside, completely or at least partially,within the computer-readable storage medium 1216, system memory 1206and/or within the processor(s) 1230 during execution thereof by theelectronic device 1200, the system memory 1206 and the processor(s) 1230also constituting computer-readable media. The electronic device 1200may also include one or more input devices 1218 (keyboard, mouse device,specialized selection keys, etc.) and one or more output devices 1220(displays, printers, audio output mechanisms, etc.).

The electronic device 1200 further includes a modem 1222 to allow theelectronic device 1200 to communicate via wireless connections (e.g.,such as provided by the wireless communication system) with othercomputing devices, such as remote computers, an item providing system,and so forth. The modem 1222 can be connected to one or more radiofrequency (RF) modules 1286. The RF modules 1286 may be a WLAN module, aWAN module, wireless personal area network (WPAN) module, GlobalPositioning System (GPS) module, or the like. The antenna structures(antenna(s) 1284, 1285, 1287) are coupled to the front-end circuitry1290, which is coupled to the modem 1022. The front-end circuitry 1290may include radio front-end circuitry, antenna switching circuitry,impedance matching circuitry, or the like. The antennas 1284 may be GPSantennas, Near-Field Communication (NFC) antennas, other WAN antennas,WLAN or PAN antennas, or the like. The modem 1222 allows the electronicdevice 1200 to handle both voice and non-voice communications (such ascommunications for text messages, multimedia messages, media downloads,web browsing, etc.) with a wireless communication system. The modem 1222may provide network connectivity using any type of mobile networktechnology including, for example, Cellular Digital Packet Data (CDPD),General Packet Radio Service (GPRS), EDGE, Universal MobileTelecommunications System (UMTS), Single-Carrier Radio TransmissionTechnology (1×RTT), Evaluation Data Optimized (EVDO), High-SpeedDown-Link Packet Access (HSDPA), Wi-Fi®, Long Term Evolution (LTE) andLTE Advanced (sometimes generally referred to as 4G), etc.

The modem 1222 may generate signals and send these signals to antenna(s)1284 of a first type (e.g., WLAN 5 GHz), antenna(s) 1285 of a secondtype (e.g., WLAN 2.4 GHz), and/or antenna(s) 1287 of a third type (e.g.,WAN), via front-end circuitry 1290, and RF module(s) 1286 as descriedherein. Antennas 1284, 1285, 1287 may be configured to transmit indifferent frequency bands and/or using different wireless communicationprotocols. The antennas 1284, 1285, 1287 may be directional,omnidirectional, or non-directional antennas. In addition to sendingdata, antennas 1284, 1285, 1287 may also receive data, which is sent toappropriate RF modules connected to the antennas. One of the antennas1284, 1285, 1287 may be any combination of the antenna structuresdescribed herein.

In one embodiment, the electronic device 1200 establishes a firstconnection using a first wireless communication protocol, and a secondconnection using a different wireless communication protocol. The firstwireless connection and second wireless connection may be activeconcurrently, for example, if an electronic device is receiving a mediaitem from another electronic device via the first connection) andtransferring a file to another electronic device (e.g., via the secondconnection) at the same time. Alternatively, the two connections may beactive concurrently during wireless communications with multipledevices. In one embodiment, the first wireless connection is associatedwith a first resonant mode of an antenna structure that operates at afirst frequency band and the second wireless connection is associatedwith a second resonant mode of the antenna structure that operates at asecond frequency band. In another embodiment, the first wirelessconnection is associated with a first antenna structure and the secondwireless connection is associated with a second antenna.

Though a modem 1222 is shown to control transmission and reception viaantenna (1284, 1285, 1287), the electronic device 1200 may alternativelyinclude multiple modems, each of which is configured to transmit/receivedata via a different antenna and/or wireless transmission protocol.

In the above description, numerous details are set forth. It will beapparent, however, to one of ordinary skill in the art having thebenefit of this disclosure, that embodiments may be practiced withoutthese specific details. In some instances, well-known structures anddevices are shown in block diagram form, rather than in detail, in orderto avoid obscuring the description.

Some portions of the detailed description are presented in terms ofalgorithms and symbolic representations of operations on data bitswithin a computer memory. These algorithmic descriptions andrepresentations are the means used by those skilled in the dataprocessing arts to convey the substance of their work most effectivelyto others skilled in the art. An algorithm is used herein, andgenerally, conceived to be a self-consistent sequence of steps leadingto a desired result. The steps are those requiring physicalmanipulations of physical quantities. Usually, though not necessarily,these quantities take the form of electrical or magnetic signals capableof being stored, transferred, combined, compared, and otherwisemanipulated. It has proven convenient at times, principally for reasonsof common usage, to refer to these signals as bits, values, elements,symbols, characters, terms, numbers, or the like.

It should be borne in mind, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. Unlessspecifically stated otherwise as apparent from the above discussion, itis appreciated that throughout the description, discussions utilizingterms such as “inducing,” “parasitically inducing,” “radiating,”“detecting,” determining,” “generating,” “communicating,” “receiving,”“disabling,” or the like, refer to the actions and processes of acomputer system, or similar electronic computing device, thatmanipulates and transforms data represented as physical (e.g.,electronic) quantities within the computer system's registers andmemories into other data similarly represented as physical quantitieswithin the computer system memories or registers or other suchinformation storage, transmission or display devices.

Embodiments also relate to an apparatus for performing the operationsherein. This apparatus may be specially constructed for the requiredpurposes, or it may comprise a general-purpose computer selectivelyactivated or reconfigured by a computer program stored in the computer.Such a computer program may be stored in a computer readable storagemedium, such as, but not limited to, any type of disk including floppydisks, optical disks, Read-Only Memories (ROMs), compact disc ROMs(CD-ROMs) and magnetic-optical disks, Random Access Memories (RAMs),EPROMs, EEPROMs, magnetic or optical cards, or any type of mediasuitable for storing electronic instructions.

The algorithms and displays presented herein are not inherently relatedto any particular computer or other apparatus. Various general-purposesystems may be used with programs in accordance with the teachingsherein, or it may prove convenient to construct a more specializedapparatus to perform the required method steps. The required structurefor a variety of these systems will appear from the description below.In addition, the present embodiments are not described with reference toany particular programming language. It will be appreciated that avariety of programming languages may be used to implement the teachingsof the present embodiments as described herein. It should also be notedthat the terms “when” or the phrase “in response to,” as used herein,should be understood to indicate that there may be intervening time,intervening events, or both before the identified operation isperformed.

It is to be understood that the above description is intended to beillustrative, and not restrictive. Many other embodiments will beapparent to those of skill in the art upon reading and understanding theabove description. The scope of the present embodiments should,therefore, be determined with reference to the appended claims, alongwith the full scope of equivalents to which such claims are entitled.

What is claimed is:
 1. A wireless device comprising: at least tworadios; at least two radio frequency (RF) ports; and an impedancedetection circuit coupled to the at least two radios, wherein theimpedance detection circuit is configured to: measure a first receivesignal strength indicator (RSSI) value of a first reflected signal, thefirst reflected signal corresponding to a first signal sent by one ofthe at least two radios; determine that the first RSSI value exceeds athreshold, the threshold representing an impedance mismatch condition ator beyond at least one of the two RF ports; and send first data to asecond device indicative of the impedance mismatch condition.
 2. Thewireless device of claim 1, wherein the impedance detection circuitcomprises: switching circuitry coupled to the at least two radios andthe at least two RF ports; and a bi-directional RF coupler coupled tothe switching circuitry, the bi-directional RF coupler comprising afirst port, a second port, a third port, and a fourth port, wherein: theswitching circuitry, in a first mode, i) couples a first radio of the atleast two radios to the first port, a first RF port of the at least twoRF ports to the third port, and a second radio of the at least tworadios to the second port, and ii) decouples a second RF port of the atleast two RF ports from the fourth port; and the switching circuitry, ina second mode, iii) decouples the bi-directional RF coupler from thefirst radio, the second radio, the first RF port, and the second RF portand iv) couples the first radio to the first RF port and the secondradio to the second RF port.
 3. The wireless device of claim 1, furthercomprising: a processing device coupled to the at least two radios andthe impedance detection circuit, wherein the processing device is to:receive a request from the second device to check for the impedancemismatch condition at or beyond any one of the at least two RF ports,wherein the impedance mismatch condition is caused by v) an antennabeing disconnected from the one of the at least two RF ports or vi) aphysical attribute of an RF cable, which is coupled between the antennaand the one of the at least two RF ports, the physical attribute causingmalfunction of the RF cable; send a control signal to the impedancedetection circuit that causes the impedance detection circuit to switchfrom a second mode to a first mode; instruct a first radio of the atleast two radios to send the first signal via the antenna; instruct asecond radio of the at least two radios to measure the first RSSI valueof the first reflected signal; and receive a command from the seconddevice to disable the first radio.
 4. The wireless device of claim 1,further comprising: a processing device coupled to the at least tworadios and the impedance detection circuit, wherein the processingdevice is to: instruct a first radio of the at least two radios to sendthe same first signal via an antenna in each channel in a set ofchannels; instruct a second radio of the at least two radios to measurea RSSI value for each channel in the set of channels; determine aphysical distance between a first RF port of the at least two RF portsand a location where the impedance mismatch condition occurs using theRSSI values for the set of channels; and sends second data to the seconddevice, the second data comprising a value representing the physicaldistance.
 5. The wireless device of claim 1, wherein the impedancedetection circuit comprises: an RF coupler coupled between the at leasttwo radios and the at least two RF ports, wherein the RF couplercomprises: a first port coupled to a first radio of the at least tworadios; a second port coupled to a second radio of the at least tworadios, wherein the second radio is to receive the first reflectedsignal at the second port; a third port coupled to a first RF port ofthe at least two RF ports; and a fourth port coupled to a second RF portof the at least two RF ports.
 6. The wireless device of claim 5, whereinthe impedance detection circuit further comprises: first radio frequencyfront-end (RFFE) circuitry; second RFFE circuitry; a first switchcoupled to the first radio, the first port, and the first RFFEcircuitry; a second switch coupled to the second radio, the second port,and the second RFFE circuitry; a third switch coupled to the first RFFEcircuitry, the third port, and the first RF port; and a fourth switchcoupled to the second RFFE circuitry, the fourth port, and the second RFport.
 7. The wireless device of claim 1, wherein the impedance detectioncircuit is further configured to: measure a second RSSI value of asecond reflected signal, the second reflected signal corresponding to asecond signal sent by a different one of the at least two radios;determine that the second RSSI value exceeds the threshold indicative ofa second impedance mismatch condition; and send second data to thesecond device indicative of the second impedance mismatch condition. 8.A method comprising: measuring, by an impedance detection circuitcoupled to at least two radios and at least two radio frequency (RF)ports, a first receive signal strength indicator (RSSI) value of a firstreflected signal, the first reflected signal corresponding to a firstsignal sent by one of the at least two radios; determining that thefirst RSSI value exceeds a threshold, the threshold representing animpedance mismatch condition at or beyond at least one of two RF ports;and sending first data to a second device indicative of the impedancemismatch condition.
 9. The method of claim 8, further comprising:receiving second data from the second device, the second data comprisesa request to check for the impedance mismatch condition; coupling an RFcoupler between the at least two radios and the at least two RF ports;causing the one of the at least two radios to send the first signal; andcausing another one of the at least two radios to measure the first RSSIvalue of the first reflected signal, wherein the impedance mismatchcondition is caused by i) an antenna being disconnected from the one ofat least two RF ports or ii) a physical attribute of an RF cable coupledbetween the antenna and the one of the at least two RF ports.
 10. Themethod of claim 8, further comprising: receiving second data from thesecond device, the second data comprises a scheduled time for a checkfor the impedance mismatch condition; setting a first radio of the atleast two radios to operate in a transmit (TX) mode and a second radioof the at least two radios to operate in a receive (RX) mode responsiveto the scheduled time; and setting switching circuitry to operate in afirst mode, wherein causing the first radio to send the first signal andcausing the second radio to measure the first RSSI value are performedwhile the switching circuitry is set to operate in the first mode. 11.The method of claim 8, further comprising: setting switching circuitryto operate in a first mode in which an RF coupler is coupled between theat least two radios and the at least two RF ports; and setting theswitching circuitry to operate in a second mode in which the RF coupleris decoupled from the at least two radios and the at least two RF ports.12. The method of claim 8, further comprising: causing a first radio ofthe at least two radios to send a plurality of signals in a channelsweep, wherein each of the plurality of signals has a differentfrequency in a channel; causing a second radio of the at least tworadios to measure a plurality of RSSI values, each of the plurality ofRSSI values corresponding to a reflected signal associated with each ofthe plurality of signals; determining a reflection distance between oneof the at least two RF ports and a location where the impedance mismatchcondition occurs using the plurality of RSSI values; and sending a valuerepresenting the reflection distance to the second device.
 13. Themethod of claim 12, further comprising: causing the second radio to senda second signal; causing the first radio to measure a second RSSI valueof a second reflected signal, the second reflected signal correspondingto the second signal sent by the second radio; and determining that thesecond RSSI value exceeds the threshold indicative of a second impedancemismatch condition, wherein the first data comprises a first indicationof the impedance mismatch condition and the second impedance mismatchcondition.
 14. The method of claim 8, further comprising: causing afirst radio of the at least two radios to send a plurality of signals ina channel sweep, wherein each of the plurality of signals has adifferent frequency in a channel; causing a second radio of the at leasttwo radios to measure a plurality of RSSI values, each of the pluralityof RSSI values corresponding to a reflected signal associated with eachof the plurality of signals; determining a reflection distance betweenone of the at least two RF ports and a location where an impedancemismatch occurs using the plurality of RSSI values; and determining thatthe impedance mismatch condition is at or beyond the at least two RFports using the reflection distance, wherein the first data comprising afirst indication of the impedance mismatch condition and a secondindication of the reflection distance.
 15. The method of claim 8,further comprising: causing a second radio of the at least two radios tosend a second signal; causing a first radio of the at least two radiosto measure a second RSSI value of a second reflected signal, the secondreflected signal corresponding to the second signal sent by the secondradio; and determining that the second RSSI value does not exceed thethreshold, wherein sending the first data comprises sending the firstdata responsive to the first RSSI value exceeding the threshold and thesecond RSSI value not exceeding the threshold.
 16. The method of claim8, further comprising: causing a first radio of the at least two radiosto send a first frame that reserves a channel for a duration of time;causing the first radio to send the first signal as a second data frameafter sending the first frame; and causing a second radio of the atleast two radios to measure the first RSSI value during the duration oftime.
 17. A first device comprising: at least two radios; at least tworadio frequency (RF) ports; an RF coupler; and a processing device,wherein the processing device is configured to: selectively couple theRF coupler between the at least two radios and the at least two RFports; measure a first receive signal strength indicator (RSSI) value ofa first reflected signal at a port of the RF coupler, the firstreflected signal corresponding to a first signal sent by one of the atleast two radios; determine that the first RSSI value exceeds athreshold, the threshold representing an impedance mismatch condition ator beyond at least one of the two RF ports; and send first data to asecond device indicative of the impedance mismatch condition.
 18. Thefirst device of claim 17, wherein the processing device is to: receive arequest from the second device to check for the impedance mismatchcondition at or beyond any one of the at least two RF ports, wherein theimpedance mismatch condition is caused by v) an antenna beingdisconnected from the one of the at least two RF ports or vi) a physicalattribute of an RF cable, which is coupled between the antenna and theone of the at least two RF ports, the physical attribute causingmalfunction of the RF cable; instruct a first radio of the at least tworadios to send the first signal via the antenna; instruct a second radioof the at least two radios to measure the first RSSI value of the firstreflected signal; and receive a command from the second device todisable the first radio.
 19. The first device of claim 17, wherein theRF coupler comprises: a first port coupled to a first radio of the atleast two radios; a second port coupled to a second radio of the atleast two radios, wherein the second radio is to receive the firstreflected signal at the second port; a third port coupled to a first RFport of the at least two RF ports; and a fourth port coupled to a secondRF port of the at least two RF ports.
 20. The first device of claim 19,further comprising: first radio frequency front-end (RFFE) circuitry;second RFFE circuitry; a first switch coupled to the first radio, thefirst port, and the first RFFE circuitry; a second switch coupled to thesecond radio, the second port, and the second RFFE circuitry; a thirdswitch coupled to the first RFFE circuitry, the third port, and thefirst RF port; and a fourth switch coupled to the second RFFE circuitry,the fourth port, and the second RF port.